Hot-chamber die casting systems and methods

ABSTRACT

Hot-chamber die casting systems for casting aluminum, copper, titanium, and their alloys, as well as other high temperature and/or reactive metals. The hot-chamber die casting system comprises an injection system that includes a cylinder, a plunger reciprocable within the cylinder, and a gooseneck that defines a passage fluidically connected to a cylinder chamber within the cylinder, wherein surfaces of the cylinder, plunger, and gooseneck that contact a molten metal during injection casting are defined by a refractory material that does not react with the molten metal, or have been treated to reduce the rate of dissolution of their surface material into the molten metal during injection casting.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/311,076, filed Mar. 21, 2016, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention generally relates to metal casting processes. The invention particularly relates to hot-chamber die casting systems, their components, and methods of manufacturing and using such systems and components.

Die casting is a widely-used process that entails the injection of a molten metal into a mold cavity under high pressure. The metal, commonly aluminum, magnesium, zinc and their alloys, and sometimes copper, titanium, and their alloys, is held under pressure within the mold cavity until it solidifies into a net shape part. The mold cavities are within dies that are typically formed of tool steels capable of withstanding the high temperatures of the molten metal. Die casting is generally considered to be a cost-effective process capable of producing precision (net-shape) products at high production rates with high metal yields per mold, from which a wide variety of metal castings can be produced to have various shapes, intricate designs, and close dimensional tolerances. Currently, die casting processes are used to produce over one-third of all metal castings.

Die casting processes are generally classified as either hot-chamber or cold-chamber die casting. The cold-chamber die casting process generally includes transferring a molten metal from a melt furnace to a holding furnace, and using an unheated injection system to draw the molten metal from the holding furnace and then inject it into a mold cavity by means of a reciprocating plunger. The process of hot-chamber die casting is similar but utilizes a heated injection system that injects the molten metal from a holding furnace of the die casting machine directly into a mold cavity. The injection system is heated as a result of being at least partially submerged in the molten metal.

Cold-chamber die casting machines can be used to cast large components from a variety of metals (the terms “metal” and “metals” are used herein to refer to pure metals and alloys thereof) that have relatively high melting temperatures. However, potential issues and limitations of cold-chamber die casting include formation of oxides during the transfer of the molten metal from the furnace to the unheated injection system, with the result that the injected molten metal may contain a substantial amount of oxides that may result in castings having diminished mechanical properties if the oxides are entrapped in the castings. Further potential issues and limitations of cold-chamber die casting include the entrapment of air in the molten metal and the formation of solids from the molten metal (e.g., in the slot sleeve or cylinder) that can become entrapped in the casting and lead to diminished mechanical properties. As a result, castings produced with cold-chamber die casting processes may contain oxide inclusions, porosity or blow holes due to entrapped air bubbles, and large fragments of solid metal formed in the injection system.

Compared to the cold-chamber process described above, hot-chamber processes are generally considered to enable higher productivity because the molten metal can be directly injected from the holding furnace into the mold. Furthermore, there is a reduced risk of entrapped air and oxides in castings because there is little if any wave formation in the injection system during metal injection, and there is little if any solid fragments formed in the injection system as it is heated at or near the temperature of the molten metal. In addition, casting temperature used in hot-chamber processes can be lower than cold-chamber die casting processes since the molten metal is not cooled by the injection system prior to entering the mold cavity and furnaces used in hot-chamber processes can be sealed to reduce the absorption of hydrogen into the molten metal and reduce the formation of oxides in the molten metal in the furnace. As such, it is well known that hot-chamber die casting processes are capable of producing castings that are superior to those produced by cold-chamber die casting processes in terms of mechanical properties and internal integrity of the castings. Therefore, hot-chamber die casting processes have been widely used for casting various metals and alloys, such as zinc and magnesium alloys, with advantages in the quality of castings and the casting productivity.

An exemplary hot-chamber die casting system and process are illustrated in FIGS. 1a and 1b . As shown, an injection system is located directly above or within a holding furnace 10. The injection system includes a power (“shot”) cylinder 12 that reciprocates a plunger 14 within a chamber 15 of a cylinder (sleeve) 16, and a gooseneck 17 that defines a gooseneck passage 18. Together the cylinder chamber 15 and gooseneck passage 18 define a “hot chamber” 20 of the injection system. The cylinder 12, plunger 14, and gooseneck 17 are heated by a molten metal 22 within the holding furnace 10 as a result of being partially submerged in the molten metal 22. As the plunger 14 travels downward through the cylinder 16 toward the passage 18 of the gooseneck 17 (FIG. 1a ), molten metal 22 within the gooseneck passage 18 is forced into a casting cavity 24 formed by dies of a mold 26 that is connected to the gooseneck 17 at its end opposite the cylinder chamber 15 and sleeve 16 (FIG. 1b ). The plunger 14 is then returned to its starting position shown in FIG. 1a to allow additional molten metal 22 to enter and refill the hot chamber 20 through an intake port 28 that is located in the side of the cylinder 16 and submersed in the molten metal 22. By locating the intake port 28 below the surface of the molten metal 22 in the holding furnace 10, the molten metal 22 drawn into the cylinder chamber 15 is less likely to include impurities, such as dross or oxides that may be floating on the surface of the molten metal 22.

In currently available commercial hot-chamber die casting systems, the gooseneck 17, cylinder 16, and plunger 14 are commonly made from ferrous alloys (which as used herein refers to alloys that contain more iron by weight, volume, or molar percent than any other individual constituent). Certain molten metals, including, but not limited to, molten aluminum, copper, titanium, and their alloys (hereinafter, “reactive metal”), are reactive with ferrous alloys in the sense that the molten metal tends to corrode and/or erode ferrous alloys during injection casting and/or ferrous alloys tend to dissolve into the molten metal during injection casting and possibly form intermetallic phases. The terms “react” and “reaction” will be used herein to refer to any one or more of these possible interactions between a reactive metal and a ferrous alloy. Hot-chamber die casting systems of the type commonly used to produce zinc and magnesium castings and equipped with a gooseneck 17 formed of cast iron, steel, or other ferrous alloys cannot be employed to die cast, for example, aluminum alloys because the injection system would not survive long in the hot-chamber die casting process. In addition, iron from injection systems tends to dissolve into high temperature molten metals and form intermetallic phases that can significantly reduce the ductility of castings. For example, iron can dissolve into aluminum alloys and form iron-aluminum intermetallic (iron aluminide, FeAl) phases.

With increasing demands on weight reduction of components used for automotive and other applications, aluminum castings have found increased use in replacing components previously formed of heavier metals and alloys. Though die casting is the main method for producing aluminum castings, cold-chamber processes are favored over hot-chamber processes for the reasons discussed above. However, aluminum castings produced by hot-chamber die casting processes would likely be much stronger and cost effective in replacing components made of heavier metals and alloys if the above-noted limitations were overcome.

As such, attempts have been made to use hot-chamber die casting processes to produce die cast aluminum components. For example, U.S. Pat. No. 3,067,146 to Gottfried, European Patent No. 0827793 to Miki et al., and Taiwan Patent Document No. 201529204 to Eguchi et al. disclose hot-chamber die casting systems which include ceramic components for casting aluminum. However, hot-chamber aluminum die casting systems that utilize ceramic liners for the gooseneck or use ceramic materials for the entirety of the gooseneck have not found wide applications because of the high financial costs and poor service life of the ceramic components. For example, ceramic materials conventionally used for such purposes have had issues with thermal fatigue. Also, the relatively low tensile properties and brittleness of ceramic materials have resulted in goosenecks formed of ceramic-based materials being prone to damage during die casting operations.

Accordingly, there is an ongoing desire for hot-chamber die casting systems, components, and methods that are capable of casting high temperature and/or reactive metals and capable of exhibiting improved operating lives relative to conventional hot-chamber systems and processes.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides hot-chamber die casting systems and methods suitable for casting aluminum, copper, titanium, and their alloys, as well as other high temperature and/or reactive metals and their alloys.

According to one aspect of the invention, a hot-chamber die casting system for injection casting a molten metal comprises an injection system adapted to be at least partially immersed in a pool of the molten metal. The injection system includes a cylinder, a plunger reciprocable within the cylinder, and a gooseneck that defines a passage fluidically connected to a cylinder chamber within the cylinder, wherein the passage and the chamber define a hot chamber of the hot-chamber die casting system. At least surfaces of the cylinder, plunger, and gooseneck that contact the molten metal during injection casting, and optionally the cylinder, plunger, and gooseneck in their entirety, are defined by one or more refractory metals that do not react with the molten metal and/or exhibit dissolution rates with the molten metal that are less than the dissolution rates of ferrous alloys with the molten metal.

According to another aspect of the invention, a hot-chamber die casting system for injection casting a molten metal comprises an injection system adapted to be at least partially immersed in a pool of the molten metal. The injection system includes a cylinder, a plunger reciprocable within a cylinder chamber within the cylinder, and a gooseneck that defines a passage fluidically connected to the cylinder chamber, wherein the passage and the chamber define a hot chamber of the hot-chamber die casting system. Each of the cylinder, plunger, and gooseneck comprises a bulk metallic material, and each of the cylinder, plunger, and gooseneck comprises refractory ceramic surfaces that contact the molten metal during injection casting and do not react with the molten metal.

According to another aspect of the invention, a hot-chamber die casting system for injection casting a molten metal comprises an injection system adapted to be at least partially immersed in a pool of the molten metal. The injection system includes a cylinder, a plunger reciprocable within the cylinder, and a gooseneck that defines a passage fluidically connected to a cylinder chamber within the cylinder, wherein the passage and the chamber define a hot chamber of the hot-chamber die casting system. The cylinder and the gooseneck are both formed of a ferrous material and surfaces of the cylinder, plunger, and gooseneck that contact the molten metal during injection casting have been treated to reduce the rate of dissolution of the ferrous material into the molten metal during injection casting.

Other aspects of the invention include methods of using systems comprising the elements described above to produce castings of high temperature and/or reactive metals.

Technical effects of the systems and methods described above preferably include the capability of casting high temperature and/or reactive metals, for example, aluminum, copper, titanium, and their alloys, while also being capable of improved operating lives relative to conventional hot-chamber die casting systems.

Other aspects and advantages of this invention will be further appreciated from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b schematically represent a conventional hot-chamber die casting system and steps in the use thereof.

FIG. 2 schematically represents an injection system comprising a one-piece cylinder and gooseneck in accordance with a nonlimiting embodiment of the invention.

FIG. 3 schematically represents an injection system comprising a shell-type cylinder and gooseneck in accordance with another nonlimiting embodiment of the invention.

FIGS. 4a through 4d graphically represent experimental results of weight loss of refractory metals and H13 steel. Weight loss was measured on samples attached on a stirrer at linear speeds given in the x-axis of the diagrams. The samples were submerged into molten A380 aluminum alloy held at 650° C. for various times (10 to 40 min.). FIG. 4a : H13 vs. Ti-6Al-4V. FIG. 4b : W vs. Ti-6Al-4V. FIG. 4c : Mo vs. W. FIG. 4d : Nb vs. Mo.

FIG. 5 graphically represents a relationship between percent dissolution and submerge time in molten A380 aluminum alloy for H13 samples with six different surface conditions. The temperature of the molten A380 alloy was 650+/−51° C. and the flow rate of the molten A380 alloy was 2.41 m/s.

FIG. 6 represents soldering area fraction (“Reaction Area”) of different coatings as a function of dipping time (“Time”) when coated samples were subjected to high intensity ultrasonic vibration in a molten A380 aluminum alloy.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides hot-chamber die casting systems for casting of aluminum and its alloys, as well as other high temperature metals such as copper, titanium, and their alloys. In particular, the systems include injection systems having a cylinder, plunger, and gooseneck that are capable of surviving contact with molten high temperature and/or reactive metals and provide the ability to cast products therewith. Further, the present invention provides methods of manufacturing and using the hot-chamber die casting systems and their components.

FIGS. 2 and 3 schematically represent two injection systems suitable for use in casting high temperature metals, such as aluminum, copper, titanium, and their alloys. For convenience, identical reference numerals are used in FIGS. 2 and 3 to denote the same or functionally equivalent elements. Each injection system shown in FIGS. 2 and 3 comprises a cylinder 116, a plunger 114 reciprocable within a chamber 115 of the cylinder 116, and a gooseneck 117 that defines a passage 118 fluidically connected to the cylinder chamber 115. An inlet 128 is provided in a sidewall of the cylinder 116, through which a molten metal (not shown) is able to enter a “hot chamber” 120 defined by the gooseneck passage 118 and the cylinder chamber 115. Hot-chamber die casting systems comprising these components may function in substantially the same manner as described previously in relation to the hot-chamber die casting system of FIGS. 1a and 1b . For example, the plunger 114 may be reciprocated within the chamber 115 of the cylinder 116 to force molten metal from a holding furnace (not shown in FIGS. 2 and 3), into the inlet 128, through the hot chamber 120, through an outlet 119 in the gooseneck 117, and into a cavity of a mold (not shown in FIGS. 2 and 3). As such, the following discussion will focus primarily on certain aspects of the injection systems represented in FIGS. 2 and 3, whereas other aspects not discussed in any detail may be, in terms of structure, function, materials, etc., essentially as was described for the system of FIGS. 1a and 1b . It should be noted that the drawings are drawn for purposes of clarity when viewed in combination with the following description, and therefore are not necessarily to scale.

FIG. 2 represents an injection system in which the cylinder 116 and gooseneck 117 are part of a one-piece (unitary) construction. The cylinder 116 and gooseneck 117 are preferably formed of a single composition, preferably a metal or alloy, that is capable of surviving prolonged contact with molten high temperature metals, and particularly an aforementioned molten “reactive” metal, i.e., a molten metal that tends to corrode and/or erode ferrous alloys during holding and injection casting and/or ferrous alloys tend to dissolve into the molten metal during holding and injection casting and possibly form intermetallic phases. The plunger 114 is also preferably formed of one or more metals that is/are capable of surviving prolonged contact with molten high temperature metals, and particularly an aforementioned molten “reactive” metal.” In particular, the cylinder 116, gooseneck 117, and plunger 114 may be formed of one or more materials that consist of or include a refractory metal, including but not limited to niobium, molybdenum, tantalum, tungsten, rhenium, titanium, vanadium, chromium, zirconium, hafnium, ruthenium, rhodium, osmium, iridium, and alloys thereof, as a majority constituent of the material. Such refractory metals are substantially nonreactive and/or have a substantially lower dissolution rate in comparison to materials commonly used in the hot-chamber die casting industry, for example, ferrous alloys such as H13 steel and cast irons. Furthermore, the cylinder 116, gooseneck 117, and/or the plunger 114 made of aforementioned refractory metals may have with their surfaces coated with a protective coating, for example, using a surface coating process such as physical vapor deposition (PVD) or chemical vapor deposition (CVD), to reduce or prevent oxidation and/or to further reduce the dissolution rate in the molten metal or alloy to be cast. Alternatively, the cylinder 116, gooseneck 117, and/or the plunger 114 may be formed of more conventional die casting mold materials, such as H13 steel, whose surfaces have been treated to be more resistive to dissolution by a molten high temperature and/or reactive metal. Suitable surface treatments include, but are not limited to, nitriding (ion plasma nitriding) and carbo-nitriding (ion plasma carbo-nitriding). Yet another alternative is to form the gooseneck 117, cylinder 116, and/or plunger 114 of a more conventional die casting mold material, such as H13 steel, and deposit a surface coating thereon of a material that is more resistive to dissolution by a molten high temperature and/or reactive metal. Suitable coating materials and deposition methods include, but are not limited to, chromium carbide (CrC) or W—Cr—Co deposited by high velocity air fuel (HVAF). Preferably, the cylinder 116, gooseneck 117, and/or the plunger 114 are formed of a material, have surfaces formed of a material, or have surfaces treated such that their surfaces have a dissolution rate that is equal to or less than the dissolution rate of titanium in a molten pool of aluminum.

FIG. 3 represents an injection system whose cylinder 116 and gooseneck 117 are again part of a one-piece (unitary) construction, but modified to have a shell-type configuration as a result of the gooseneck 117 and the cylinder 116 each being formed of at least two materials, one of which is designated a shell material 130 and another designated as a bulk material 132 located within the interior of the shell material 130. Preferably, only the shell material 130 is intended to contact the high temperature or reactive metal during injection casting, such that the bulk material 132 does not as a result of the shell material 130 effectively forming an outer layer on the bulk material 132. The use of the bulk material 132 allows for the use of materials that are not required to be resistant to the molten metal and may reduce the cost of producing the injection system while obtaining high mechanical properties and longer service life for the injection system. In contrast, the shell material 130 is capable of surviving prolonged contact with molten high temperature metals, and particularly a molten reactive metal. As such, the shell material 130 may be formed of a material that consists of or includes a refractory metal, such as those described for the embodiment of FIG. 2. Alternatively, the shell material 130 may be formed of a material that consists of or includes a refractory ceramic material, including but not limited to FeN, FeNC, CrWN, AlCrN, TiN, carbon-based materials including carbides such as VC and WC, and combinations thereof as a majority constituent of the shell material 130. The bulk material 132 may be any suitable material capable of providing support for the shell material 130 thereon, for example, steel. However, if the shell material 130 is formed of a refractory metal and is sufficiently thick to be mechanically strong enough to withstand the die casting process, the bulk material 132 could be omitted, in other words, the one-piece (unitary) construction of the injection system comprising the gooseneck 117 and cylinder 116 is hollow rather than the interior of the shell material 130 being filled with the bulk material 132.

The injection systems of FIGS. 2 and 3 may be produced with an additive manufacturing process. The additive manufacturing process could include the use of a high energy heat source, such as laser or electron beams, to melt wire or powder feed stock to build the gooseneck 117 and cylinder 116 in their entirety (FIG. 2) or build the shell and/or bulk materials 130 and 132 (FIG. 3) in a layer-by-layer or continuous process.

The injection system of FIG. 3 may be produced by initially providing the bulk material 132 as a core, and then applying a layer of the shell material 130 thereto using a suitable process, for example, physical vapor deposition, chemical vapor deposition, laser cladding, thermal spraying, additive manufacturing, explosive bonding, or other suitable layer application or deposition process. In the case of explosive bonding, the shell material 130 may be bonded to the bulk material 132 using impact generated by explosion of gun powders applied on a volume of the shell material 130. Alternatively, the shell material 130 may be formed as a hollow mold and the bulk material 132 subsequently cast within the cavity of the shell material 130, for example, through a suitable injection process.

By forming the cylinder 116, gooseneck 117, and/or plunger 114 entirely of refractory materials and/or their surfaces treated to be more resistive to a molten high temperature and/or reactive metal (FIG. 2) or to have a shell material 130 of a refractory material (FIG. 3), it is believed that the hot-chamber die casting system will have an improved operating life and be capable of producing products of improved quality. Nonlimiting embodiments of the invention will now be described in reference to experimental investigations leading up to the invention.

FIGS. 4a through 4d are graphs that show measured weight losses of samples formed of metals and alloys in molten A380 aluminum alloy, which is a widely-used die casting alloy. Samples were attached on a stirring apparatus and submerged for various durations (10, 20, and 40 minutes) in the molten A380 alloy held at 650° C. The stirring apparatus was operated at various linear speeds indicated in the x-axis of the graphs. Weight losses of the samples were measured after the indicated durations. The samples were formed of H13 (FIG. 4a ), Ti-6Al-4V (FIG. 4a and FIG. 4b ; labeled as “Ti”), Anviloy® (a tungsten alloy commercially available from Astaras, Inc.; FIG. 4b and FIG. 4c ; labeled as “W”), Mo (FIG. 4c and FIG. 4d ), and Nb-1Zr (FIG. 4d ; labeled as “Nb”). The nominal composition (weight percent) of the A380 alloy was 7.5-9.5 silicon (Si), 3.0-4.0 copper (Cu), 3.0 or less iron (Fe), 0.5 or less manganese (Mn), and the remaining balance being aluminum (Al). H13 steel was used as a baseline and had a nominal composition (weight percent) of 0.40 carbon (C), 1.00 silicon (Si), 0.020 or less phosphorus (P), 0.003 or less sulfur (S), 5.3 chromium (Cr), 1.40 molybdenum (Mo), 1.0 vanadium (V), and the remaining balance being iron (Fe). Experimental results presented in FIGS. 4a through 4d indicated that the dissolution rate, or weight loss, of H13 steel in molten A380 alloy was 3.4 times higher than that of Ti-6Al-4V, 136 times higher than that of Anviloy®, 366 times higher than that of molybdenum, and 917 times higher than that of Nb-1Zr alloy. Furthermore, no brittle iron aluminide or other iron-based intermetallic phases were formed in the aluminum castings made during the investigations. Consequently, the use of Ti-6Al-4V, Anviloy®, molybdenum, and Nb-1Zr alloy to form the entirety of the gooseneck 117 and cylinder 116 of an injection system, or at least a shell material 130 thereof so that the molten metal only contacts surfaces formed by these refractory materials, can significantly reduce the weight loss and extend the service life of these components in molten A380 alloy.

FIG. 5 and Table 1 show relationships between the percent dissolution and submerge time in a melt of the A380 alloy for H13 samples with six different surface treatment conditions using a stir test method. The temperature of the molten A380 alloy was 650+/−51° C. and the flow rate of the molten metal was 2.41 m/s. Details of the experimental conditions are given in Q. Han et al., Dissolution of H13 Steel in Molten Aluminum, NADCA Transaction, 2015, Paper T15, Indianapolis, Ind., USA, incorporated herein by reference. These experimental results suggested that surface treatments such as ion plasma nitriding and ion plasma carbo-nitriding and surface coatings such as chromium carbide or W—Cr—Co deposited by HVAF significantly reduced the dissolution amount of H13 samples. Consequently, surface treatment methods of these types can be used for protecting injection systems employed to die cast molten high temperature and/or reactive metals and having components formed of ferrous metals. Boriding was less effective in reducing the weight loss of H13 steel sample under the stirring test.

TABLE 1 Surface finishing processes. Ion Ion Plasma HVAF: No Plasma Carbide Chromium W-Co- Coating Nitride Nitride Boriding Carbide Cr (NC) (IPN) (IPCN) (B) (CC) (HVAF) 10 min 3 0.06 0.05 2 0.1 1 20 min 11 0.09 0.07 6 0.2 1 40 min 22 0.11 0.08 15 1 6

FIG. 6 shows relationships of “Reaction Area” and dipping times for H13 samples covered with a layer of one of four different ceramic coatings deposited by PVD. The term “Reaction Area” in FIG. 6 refers to soldering area fraction (SAF), which in the investigation was the ratio of the soldered surface area (the surface area where a coating is damaged by a molten metal) to the total surface area of the coating contacted by the molten metal. The ceramic materials were BALINIT® ALCRONA (AlCrN), BALINIT® D (CrN), BALINIT® FUTURA NANO (TiAlN), and BALINIT® LUMENA (TiAlN), all commercially available from Balzers, Inc. or OC Oerlikon Corporation AG. Published properties of the ceramic coating materials are given in Table 2. Experimental results given in Table 3 were obtained under cavitation conditions in an accelerated soldering test disclosed in Q. Han et al., Accelerated Method for Testing Soldering Tendency of Core Pins, International Journal of Cast Metals Research, 2010, vol. 23, no. 5, pp. 296-302, incorporated herein by reference. Samples (¾ inch (19 mm) diameter) were submerged in molten A380 alloy held in a graphite crucible at 665+/−15° C. High intensity ultrasonic vibration was applied through the sample to the molten A380 alloy to create cavitation conditions which usually occur under die casting conditions. The power of the ultrasonic vibration was 1.5 kW, the amplitude of ultrasonic vibration at the end of each sample was 16 micrometer, and the frequency of the ultrasonic vibration was 20 kHz. The Reaction Area (SAF) value of the uncoated H13 sample was one at an elapsed time of one second, indicating that the surface of the sample was totally covered by a soldered layer. It took almost sixty seconds or longer to reach a SAF value of one for each of the coated samples. These results suggested that a chemical reaction between the molten A380 alloy and the coated H13 sample started on the coated samples much later than that on the uncoated H13 samples. Of the four commercial PVD coatings, BALINIT® LUMENA lasted longest when subjected to high intensity ultrasonic vibration. It took almost thirty to sixty seconds to reach a SAF value of one for the samples coated with a BALINIT® ALCRONA, BALINIT® D (CrN), or BALINIT® FUTURA NANO, respectively, and more than 240 seconds to reach a SAF value of 0.74 for the sample coated with the BALINIT® LUMENA coating. As such, the PVD coatings tested significantly reduced the dissolution rates of H13 in the molten aluminum alloy, and such an effect would also be expected for other aluminum alloys. Consequently, a ceramic layer can substantially reduce the dissolution rates of the gooseneck 117 or cylinder materials in molten aluminum and molten aluminum alloys.

TABLE 2 Die casting coatings used in investigations. Coating BALINIT ® BALINIT ® FUTURA BALINIT ® ALCRONA BALINIT ®D NANO LUMENA Material AlCrN CrN TiAlN TiAlN Hardness 3200 1750 3300 3400 (HV) Thickness 1-5 1-6 1-4 8-15 (Microns) Max Temp 1080 1300 1600 1650 (° C.) Coating Violet Grey Silver Grey Violet Grey Violet Grey Color Coating Monolayer Monolayer Nano Layer Nano Layer Type

TABLE 3 Soldering area fractions (SAFs) of commercial coatings after given dipping times. Dipping Time (seconds) Coatings 1 5 10 15 30 60 120 240 H13 Steel 1 BALINIT ® 0.14 0.41 0.56 0.97 1 ALCRONA BALINIT ®D 0.32 0.38 0.40 1 1 BALINIT ® 0.14 0.22 0.58 0.92 0.97 FUTURA NANO BALINIT ® 0.003 0.03 0.15 0.74 LUMENA

While the invention has been described in terms of specific or particular embodiments and investigations, it is apparent that other forms could be adopted by one skilled in the art. For example, the hot-chamber die casting system and its components could differ in appearance and construction from the embodiments described herein and shown in the drawings, functions of certain components of the system could be performed by components of different construction but capable of a similar (though not necessarily equivalent) function, and appropriate materials could be substituted for those noted. Accordingly, it should be understood that the invention is not limited to any embodiment described herein or illustrated in the drawings. In addition, the invention encompasses additional or alternative embodiments in which one or more features or aspects of the different disclosed embodiments may be combined. It should also be understood that the phraseology and terminology employed above are for the purpose of describing the disclosed embodiments and investigations, and do not necessarily serve as limitations to the scope of the invention. Therefore, the scope of the invention is to be limited only by the following claims. 

1. A hot-chamber die casting system for injection casting a molten metal, the hot-chamber die casting system having an injection system that is at least partially immersed in a pool of the molten metal, the injection system comprising: a cylinder having a chamber therein; a plunger reciprocable within the chamber of the cylinder; and a gooseneck defining a passage fluidically connected to the chamber within the cylinder, the passage and the chamber defining a hot chamber of the hot-chamber die casting system; wherein at least surfaces of the cylinder, plunger, and gooseneck that contact the molten metal during injection casting, or optionally the cylinder, plunger, and gooseneck in their entirety, are defined by one or more refractory metals or alloys thereof that do not react with the metal and/or exhibit dissolution rates with the molten metal that are less than the dissolution rates of ferrous alloys with the metal.
 2. The hot-chamber die casting system of claim 1, wherein each of the cylinder, plunger, and gooseneck consists of the one or more refractory metals or alloys thereof.
 3. The hot-chamber die casting system of claim 1, wherein each of the cylinder, plunger, and gooseneck comprises a bulk material and a shell material on the bulk material that defines the surfaces thereof that contact the molten metal during injection casting.
 4. The hot-chamber die casting system of claim 3, wherein the shell material is a coating applied to surfaces of the bulk material.
 5. The hot-chamber die casting system of claim 3, wherein the shell material is produced to have a cavity therein that is filled by injecting a liquid volume of the bulk material therein.
 6. A method of using the hot-chamber die casting system of claim 1, the method comprising: at last partially immersing the injection system in a pool of the molten metal; and actuating the plunger to force a molten volume of the molten metal through the passage of the gooseneck and into a die mold cavity.
 7. The method of claim 6, wherein the molten metal is aluminum, copper, titanium, or an aluminum alloy, copper alloy, or titanium alloy.
 8. A casting formed by the method of claim
 6. 9. A hot-chamber die casting system for injection casting a molten metal, the hot-chamber die casting system having an injection system that is at least partially immersed in a pool of the molten metal, the injection system comprising: a cylinder having a chamber therein; a plunger reciprocable within the chamber of the cylinder; and a gooseneck defining a passage fluidically connected to the chamber within the cylinder, the passage and the chamber defining a hot chamber of the hot-chamber die casting system; wherein each of the cylinder, plunger, and gooseneck comprises a bulk metallic material, and each of the cylinder, plunger, and gooseneck comprises refractory ceramic surfaces that contact the molten metal during injection casting and do not react with the molten metal.
 10. The hot-chamber die casting system of claim 9, wherein each of the cylinder, plunger and gooseneck comprises a shell material on the bulk metallic material thereof that defines the refractory ceramic surfaces thereof that contact the molten metal during injection casting, wherein the shell material comprises the refractory ceramic material.
 11. The hot-chamber die casting system of claim 10, wherein the shell material is a coating applied to surfaces of the bulk metallic material.
 12. The hot-chamber die casting system of claim 10, wherein the shell material is produced to have a cavity therein that is filled by injecting a liquid volume of the bulk metallic material therein.
 13. A method of using the hot-chamber die casting system of claim 9, the method comprising: at last partially immersing the injection system in a pool of the molten metal; and actuating the plunger to force a molten volume of the molten metal through the passage of the gooseneck and into a die mold cavity.
 14. The method of claim 13, wherein the molten metal is aluminum, copper, titanium, or an aluminum, copper or titanium alloy.
 15. A casting formed by the method of claim
 13. 16. A hot-chamber die casting system for injection casting a molten metal, the hot-chamber die casting system having an injection system that is at least partially immersed in a pool of the molten metal, the injection system comprising: a cylinder having a chamber therein; a plunger reciprocable within the chamber of the cylinder; and a gooseneck defining a passage fluidically connected to the chamber within the cylinder, the passage and the chamber defining a hot chamber of the hot-chamber die casting system; wherein the cylinder, plunger, and gooseneck are each formed of a ferrous material and surfaces of the cylinder, plunger, and gooseneck that contact the molten metal during injection casting have surface treatments to reduce the rate of dissolution of the ferrous material into the molten metal during injection casting.
 17. The hot-chamber die casting system of claim 16, wherein the surface treatments are nitride or carbo-nitride surface treatments.
 18. A method of using the hot-chamber die casting system of claim 16, the method comprising: at last partially immersing the injection system in a pool of the molten metal; and actuating the plunger to force a molten volume of the molten metal through the passage of the gooseneck and into a die mold cavity.
 19. The method of claim 18, wherein the molten metal is aluminum, copper, titanium, or an aluminum, copper, or titanium alloy.
 20. A casting formed by the method of claim
 18. 